add ability to select in scan what is todo with existing services (Clear before scan)

add ability to select in scan what is todo with existing services (Clear before scan)
a) "yes" means remove all services and transponders for this sat position / all selected sat positions
b) "no" means hold all services and transponders for this sat position / all selected sat positions
   this resets all old new found flags (incremental scan)
c) "yes (hold feeds) means the same as a) but hold all feed services/transponders